Chemoprevention of keratinocyte carcinoma and actinic keratosis in solid-organ transplant recipients: Systematic review and meta-analyses

Abstract

To the Editor: Skin cancers account for 40% of malignancies in solid-organ transplant recipients (SOTRs), who have an 80-fold increased risk of squamous cell carcinoma (SCC) and a 16-fold increased risk of basal cell carcinoma (BCC). Systemic chemoprevention is one method to mitigate this amplified risk. Acitretin, for instance, has been used to prevent keratinocyte carcinomas (KC) and actinic keratoses (AK) in SOTRs since 1995,1Bavinck J.N. Tieben L.M. Van der Woude F.J. et al.Prevention of skin cancer and reduction of keratotic skin lesions during acitretin therapy in renal transplant recipients: a double-blind, placebo-controlled study.J Clin Oncol. 1995; 13: 1933-1938Crossref PubMed Google Scholar but its adverse effects include mucositis, liver and lipid abnormalities, and teratogenicity.2George R. Weightman W. Russ G.R. et al.Acitretin for chemoprevention of non-melanoma skin cancers in renal transplant recipients.Australas J Dermatol. 2002; 43: 269-273Crossref PubMed Scopus (130) Google Scholar Nicotinamide, an amide form of vitamin B3, is a newer chemoprophylaxis with fewer adverse effects.3Chen A.C. Martin A.J. Dalziell R.A. et al.A phase II randomized controlled trial of nicotinamide for skin cancer chemoprevention in renal transplant recipients.Br J Dermatol. 2016; 175: 1073-1075Crossref PubMed Scopus (61) Google Scholar Here we report results of a pairwise and network meta-analyses to summarize the current evidence regarding chemoprevention. We selected studies that analyzed the efficacy of systemic chemoprevention to prevent KC/AK in patients who are SOTRs or have a history of 2 or more KCs, or both. We limited our search to placebo-controlled, randomized control trials (RCTs) that reported the number of new KC/AK in both arms. Two authors (L.Y.T., S.Y.C.T.) independently conducted the literature search, screened titles and abstracts for eligibility, and extracted data. Statistical synthesis was performed with RevMan 5.3 software (The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen, Denmark). After the literature search, 6 RCTs with 734 patients were included in the quantitative synthesis (Appendix A, available via Mendeley at https://doi.org/10.17632/m6z2fzkkxn.2). Of the 6 RCTs, 3 studies with 580 patients (range, 17-192 patients) compared nicotinamide to placebo, and 3 studies with 154 patients (range, 19-35 patients) compared acitretin to placebo. Pairwise meta-analysis of all 6 RCTs using a random-effects model demonstrated a significant risk reduction with chemoprevention (Fig 1). The overall mean difference was 0.855 (95% confidence interval, 0.365-1.345; P < .001). In addition, acitretin and nicotinamide were both efficacious, with a combined mean difference of 0.792 (95% confidence interval, 0.298-1.286; P = .00168) for acitretin and a combined mean difference of 4.239 (95% confidence interval, 0.611-7.866; P = .0220) for nicotinamide. A network meta-analysis comparing nicotinamide and acitretin found no significant difference between the 2 treatments (Fig 2, Appendix B).Fig 1Forest plot of the pairwise meta-analysis of randomized controlled trials. The squares indicate the mean difference and are proportional to the weights used in the meta-analysis. The horizontal lines represent the 95% confidence interval (CI). The diamond indicates the weighted mean difference, and the lateral tips of the diamond indicate the associated 95% CI.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Fig 2Network graph and league table of the network meta-analysis. Mean differences and 95% confidence intervals are calculated using a random-effects model. A mean difference >1 means the top-left treatment is better.View Large Image Figure ViewerDownload Hi-res image Download (PPT) This meta-analysis does not address the optimal dosages of the drugs or the frequency of adverse effects. In addition, owing to the limited numbers of eligible RCTs, we are unable to investigate how chemoprevention is influenced by the duration or type of transplantation, duration of systemic chemoprevention, or existing immunosuppressive regimens. Moving forward, topical chemoprevention may be a suitable alternative to systemic chemoprophylaxis in SOTRs. Notably, large RCTs have evaluated topical chemoprevention for actinic keratosis. For instance, the Veterans Affairs Keratinocyte Carcinoma Chemoprevention trial found that topical 5% 5-fluorouracil cream resulted in a 49% relative risk reduction in the number of AK after 6 months and reduced the risk of SCC requiring surgery by 75% after 1 year but did not lower the risk of BCC.4Hyemin P. Hogan D. Eilers D. et al.Long-term efficacy of topical fluorouracil cream 5% for treating actinic keratosis: a randomized clinical trial.JAMA Dermatol. 2015; 151: 952-960Crossref PubMed Scopus (69) Google Scholar,5Weinstock M.A. Thwin S.S. Siegel J.A. et al.Chemoprevention of basal and squamous cell carcinoma with a single course of fluorouracil, 5%, cream: a randomized clinical trial.JAMA Dermatol. 2018; 154: 167-174Crossref PubMed Scopus (54) Google Scholar To our knowledge, this is the first meta-analysis that statistically integrates the current evidence regarding chemoprevention of KC/AK. This study demonstrates that systemic chemoprevention with nicotinamide or acitretin is effective in lowering the risk of KC/AK. Yet, even with the advent of better chemoprevention, regular physician surveillance and sun protection are still key basic strategies that should be practiced by all SOTRs.